This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Increasing epidemiologic and experimental evidence provides compelling evidence that breast cancer risk is determined early in life. A method to monitor breast development and composition in young women and girls is currently not available because of the risk of X-ray based mammograms. Dual Energy X-ray Absorptiometry (DXA) has extremely low radiation and is commonly available. The underlying rationale of this project is that predictors of breast cancer risk may be observed during pubertal development in girls. The specific aims of this project among adult women and adolescent girls, who will be recruited as mothers and biological daughter, will be to: - Correlate breast density measured by DXA with mammographic density among adult women; - Compare the association of known breast cancer risk factors with breast density from DXA scans to their association with mammographic density; - Assess DXA breast density and Tanner stage of breast maturation among adolescent girls; - Relate DXA breast density to other observable measure of pubertal maturation; - Examine the relation between breast density measured by DXA in mothers and biological daughters Our hypotheses are as follows: 1. DXA imaging can provide a valid assessment of breast density in adult women and in young girls;2. DXA assessed breast density is associated with indicators of pubertal maturation and with known breast cancer risk factors;and 3. Due to its strong genetic component, breast density obtained from the DXA scans is correlated between mothers and biological adolescent daughters. Women at least 40 years of age with biological daughters 10-16 years of age will be recruited from Kaiser Permanente Hawaii. Expected enrollment is 50 Caucasian and 50 Asian-American or Pacific Islander pairs. The eligibility criteria are: 1. Normal mammogram during recent 6 months for adult women;2. Biological daughters willing to participate in Tanner staging;3. No condition that would interfere with study participation (e.g. cancer, paralysis, morbid obesity, breast implants);4. Mother and daughter not taking medications that may interfere with hormone levels: oral contraceptives, other sex hormones, SERMs;5. Willing to obtain DXA scans. We will calculate summary statistics to describe the distribution of age, body weight, pubertal stages, DXA measures, and mammographic density.